Tsunami debris

A line of massive boulders on the western shore of Tonga may be evidence of the most powerful volcano-triggered tsunami found to date. Up to 9 meters (30 feet) high and weighing up to 1.6 million kilograms (3.5 million pounds), the seven coral boulders are located 100 to 400 meters (300 to 1,300 feet) from the coast. The house-sized boulders were likely flung ashore by a wave rivaling the 1883 Krakatau tsunami, which is estimated to have towered 35 meters (115 feet) high.

The boulders are believed to have been tossed onto Tonga "within the past few thousand years."